Subject: The 1960 chilean tsunami

What were the main causes and overall effects of the 1960 chilean tsunami?

    The tsunami was generated the by Chile earthquake of 1960, the largest earthquake ever recorded (it was magnitude 9.6). What happened in the earthquake was that a piece of the Pacific seafloor (or strictly speaking, the Nazca Plate) about the size of California slid fifty feet beneath the continent of South America. Like a spring, the lower slopes of the South American continent offshore snapped upwards as much as twenty feet while land along the Chile coast dropped about ten feet. This change in the shape of the ocean bottom changed the shape of the sea surface. Since the sea surface likes to be flat, the pile of excess water at the surface collapsed to creat a series of waves--the tsunami.
    The tsunami, together with the coastal subsidence and flooding, caused tremendous damage along the Chile coast, where about 2,000 people died. The waves spread outwards across the Pacific. 15 hours later the waves flooded Hilo, on the island of Hawaii, where they built up to thirty feet and caused 61 deaths along the waterfront. Seven hours after that (22 hours after the earthquake) the waves flooded the coastline of Japan where ten-foot waves caused 200 deaths. The waves also caused damage in the Marquesas, in Samoa, and in New Zealand. Tide gauges throughout the Pacific measured anomalous oscillations for about three days as the waves bounced from one side of the ocean to the other.

Dr. Gerard Fryer
Hawaii Institute of Geophysics & Planetology
University of Hawaii, Honolulu, HI 96822

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